People actually thought Widow referred to herself as a monster only because she can't have kids?

The way i understood it was that they sterilized her so that she'd be less distracted during a mission since thoughts of family and a future would be the one thing that could throw off her priorities.

Saying "they modified my body to make me more efficient at killing things and feeling nothing of it" is probably valid grounds for identifying as a monster.

And if you saw Agent Carter i think monster is actually quite apposite.

A man and a woman both feel like their humanity is undermined by their inability to be a father and a mother, respectively, which feeds into their mutual fears that at the end of the day they are nothing but killing machines. In a private moment, they share those feelings with each other.

And people think that's sexist.